The invention involves a process for the control of a refrigeration system, a refrigeration system, and an expansion valve for a refrigeration system of this type.
Published German Application No. DE 40 05 728 A1 is an example of the prior art. In it, the refrigeration system is controlled as a function of superheating at the evaporator outlet. For this purpose, the expansion valve has an actuator constructed as a diaphragm which is contacted on one side by refrigerant pressure at the evaporator outlet and on the other side by a pressure corresponding to the refrigerant temperature at the evaporator outlet. This control requires that either the suction line leading to the compressor or a measuring section constructed as a capillary tube, for example, be connected to the expansion valve. This leads in many ways to restrictions in the design of the refrigeration system. In addition, a control which is not very smooth, having a greatly fluctuating superheating, frequently results.
In the known case, an additional influence, which is derived from the temperature in the line between the compressor and condenser, is superimposed on this superheating control. For this purpose, one of the two pressure cavities of the syphon diaphragm is filled with a control medium which has a heat exchange through the diaphragm with the superheated refrigerant at the outlet of the evaporator and is additionally heated by the heating element, for example a PTC-resistor.
U.S. Pat. No. 4,467,613 is another example of the prior art. This reference has a sensor located downstream of an evaporator, therefore in communication with the superheat. it also results in a control which is not smooth, and can have widely fluctuating superheating.